or Natural Philosophy. By the word physics, in its most extensive sense, we understand The science of the operations of nature, and of its productions. This definition is alone sufficient to inform us, what are the particular parts of physics, and what are the means it employs to attain its ends. Thus Natural History, or Zoology, Botany, and Mineralogy, describe those bodies that nature produces, as far as they are discernible by our senses. So Chemistry and Experimental Philosophy discover to us, at least in part, the composition of bodies, and the various alterations of which those compositions are susceptible. So General and Speculative Physics draws from all these preliminary observations, from all these matters of fact, just consequences relative to the universal laws of nature, to the properties, forces, action, and essential qualities of bodies.

The object of physics being the examination of the whole frame of nature, so far as it is visible and palpable to man, it is easily to conceive, that it must form the most extensive branch of human knowledge, seeing that the operations of nature are varied almost to infinity. To reduce this immense subject into some order, philosophers have begun by dividing all the productions of this globe into three classes, which they call kingdoms, and distinguish into the vegetable, the mineral, and animal kingdom. Botany, mineralogy, and natural history properly so called, teach therefore all that is come to the knowledge of man in each of these kingdoms. Chemistry resolves all bodies, and consequently shows the manner in which they are compounded. Philosophers have likewise discovered that the universe is composed of elements, of which there are four, Earth, Water, Fire, and Air. Experimental philosophy, by numberless essays and observations, explains the manner in which these elements operate upon each other, and the effects that they produce. The knowledge of those heavenly bodies, whose various courses fill the vast expanse of the firmament, and of their properties and courses either real or apparent, is comprised in the science of Astronomy.

All the ancient oriental nations, including the Hebrews and the Egyptians, were mere novices in physics; and their ignorance seems to prove the infancy of the world. The Greeks, men of a subtle and inquisitive genius, went further, and sometimes guessed right enough, though very rarely. Empedocles, for example, who is ranked by some among the Pythagoreans, professed the system of the four elements in nature; and added thereto two principles, which he called principium amicitiae, and principium contentiones. The first, according to him, is the cause of the coalition of beings; and the second, that of their reception or separation. Was not this derived from the same origin as the celebrated system of the attraction and repulsion of bodies? Whatever was the cause, the progress of physics has ever been slow; and we are astonished when we see ancient writers of the greatest genius, as Plutarch and a hundred others, make use of such wretched reasoning when they mention those subjects that relate to physics.

Among the Romans, Lucretius and Cicero have indeed written on these subjects; but they have only related the opinions of the Greeks, which were not worthy of great regard. Seneca and Pliny went further; and we are obliged to the latter for the useful observations which he has made on many parts of this science, although he is frequently too credulous. Pliny, moreover, does not belong to the class of dogmatic authors on physics, as he gives only an historical account of these matters.

The first ages of Christianity were the ages of darkness for all the sciences and the arts. It was not till very late, that Bacon baron of Verulam, and some of his contemporaries, produced the first sparks of those fair lights that have since blazed forth by the happy labours of their successors. Gassendus, Descartes, Rudiger, Newton, Leibnitz, Wolff, and a multitude of other celebrated philosophers, have diffused these lights over philosophy; and all these great men have at last established that method of treating it which is alone able to discover the truth. This method is perfectly simple. They begin with establishing facts by means of experiments and observations, and draw from thence consequences relative to their causes and principles. For, as soon as experience or the senses have discovered what passes in nature, the mind endeavours to discover what cannot be distinguished by the senses; that is to say, what may be the cause or the end of each phenomenon or operation in nature; and by this means it constantly combines the accuracy of observation with the sagacity and rigour of argument.

It is certain, that a diligent observation of the subjects of Mineralogy and Zoology, united with the study of Botany, affords every possible information relative to natural history in general; that is, we thereby acquire the historical knowledge of all the beings of this globe, that nature produces. Experimental Philosophy, aided by Chemistry, and several parts of the Mathematics, disclose the composition of these beings, and the springs by which nature operates in their production, and in making them produce, in their turn, the mutual effects of the elements, &c. Astronomy, of which we have in like manner treated, explains the nature of the celestial bodies and their courses; and all these various sciences, united, conduct us at last, as far as the human mind is able to proceed, to the determination of the general laws of nature in the order of the universe; from whence result universal and speculative Physics, of which it remains to give a cursory idea. This science, which for some thousand years has been justly called speculative, seeing that it has been founded altogether on vain speculations, and suppositions merely ideal, is at length supported by experiments and observations that bear the stamp of manifest demonstrations. It now forms no system, admits of no hypothesis, but such whose veracity and certainty have been previously demonstrated. For which purpose it calls to its assistance all the subordinate sciences, and makes use of their operations in the investigation and establishment of its principles. As Mineralogy, Botany, Zoology, Chemistry, Anatomy, Physiology, and almost all the other parts of Physic, Geography, Experimental Philosophy, all the particular sciences which are comprised under the general denomination of Mathematics; all these have relation to general physics, and each of them concurs more or less to furnish materials for its sublime operations. When, by the assistance of the labours of these, physics has established the veracity of facts, it then applies the most subtile, abstract, and profound ratiocination, to draw from thence just consequences, and to establish general principles, founded on these facts, relative to the universal laws of nature; to the celestial bodies, and the true order of the universe; to the elements, and their reciprocal action; to meteors; to bodies that are both visible and tangible; to the reciprocal action of palpable bodies; to the generation of beings in general, and of man in particular; to every production of nature in all the three kingdoms: in a word, it endeavours to account, as far as the weak lights of the human understanding are capable of accounting, for all the phenomena of heaven and earth. See all the abovementioned sciences generally treated in the order of the alphabet.